Chemical smog

Abstract

This article deals with urban air pollution, commonly called smog, and its impacts on ecosystems, agriculture, material substances, and human health. This should be in reference of brief description of the two types of smog (London or sulfurous smog and Los Angeles or EOLSS* smog). The chemistry of smog is reviewed with a focus on the Los Angeles or photochemical type, which is the dominant type impacting urban, regional, and global environment today. The chemical processes that form photochemical smog from the hydrocarbon and nitrogen oxide emissions of combustion processes are briefly reviewed. The importance of the formation of secondary oxidants (e.g., ozone [O3], peroxyacylnitrates [PANs]) and inorganic acids (sulfuric and nitric) in photochemical smog is stressed. These secondary oxidants and acids play important roles in the effects of smog on ecosystems and human health, as well as in agriculture and materials damage on urban, regional, and global scales. The effects of the air pollutants produced in smog formation are also reviewed. The urban-, regional-, and global-scale impacts discussed include human health effects; damage to buildings, plants, and tree foliage; crop yield reduction; visibility loss; precipitation pollution (acid rain); and radiative balance effects including urban heat islands, weather, and climate. The concept of urban climate impacts is introduced and discussed in light of the radiative properties of the gases and aerosols present in urban atmospheres due to smog formation.